Nonplanar Nanographene with a Large Conjugated π-Surface.

Conjugated π-surfaces are ubiquitous in molecules and materials. However, large π-surfaces up to a few nanometers in size are difficult to construct in an atomically precise manner. They tend to aggregate because of strong π-π interactions, resulting in notorious problems for both purification and spectroscopic investigations. Here, by contrast, we report the design, synthesis, and full characterizations of a nonplanar nanographene 1, which has a large, precise, and nonstacked π-surface. It is soluble in common organic solvents and allows for thorough investigations. The structure of 1, comprising 85 fused rings with an extended π-surface of 3 nm in size, is unambiguously confirmed by single-crystal X-ray diffraction. Unusual electronic structures, record-high near-infrared absorption, pronounced magnetic shielding, and ultrastrong heteromolecular van der Waals complexations are demonstrated, enabling us to establish a clear structure-property relationship, which has been elusive for decades. These results have broad implications for studying and understanding various phenomena and processes relevant to both discrete and interacting π-surfaces.

Synthesis and Characterization of a Cyclic Trimer of a Chiral Spirosilabifluorene.

A chiral shape-persistent macrocyclic compound (Si-[3]), designed by the C/Si substitution in the spiro-atom of spirobifluorene in the cyclic trimer (C-[3]), has been successfully synthesized in this study. The C/Si substitution made the spiro-conjugation and energy levels of HOMO and LUMO decrease. Due to the silicon substitution, the macrocyclic compound Si-[3] was able to be degraded by fluoride ions, but its reaction rate was slower than that of the unsubstituted spirosilabifluorene, showing the chemical stability of Si-[3]. Furthermore, the chiroptical properties of Si-[3] with D3-symmetric macrocyclic structure were investigated, and (P,P,P)-Si-[3] showed a high emission quantum yield (Φf=80 %) and moderate dissymmetry factor of circularly polarized luminescence (CPL) (glum,exp=-1.2×10-3). According to the time-dependent density-functional theory (TD-DFT) calculations using polarizable continuum model (PCM), the bright CPL from Si-[3] was explained by a planarization of one bisilafluorenyl moiety at the excited state, which is responsible for the almost fully-allowed radiative transition with a short emission lifetime of τf=1.89 ns.

Endoscopic Diagnosis of Epithelial Subtypes of Superficial Non-Ampullary Duodenal Epithelial Tumors using Magnifying Narrow-Band Imaging.

INTRODUCTION: Superficial non-ampullary duodenal epithelial tumors (SNADETs) include low-grade adenoma (LGA) and high-grade adenoma or carcinoma (HGA/Ca) and are classified into two different epithelial subtypes, gastric-type (G-type) and intestinal-type (I-type). We attempted to distinguish them by endoscopic characteristics including magnifying endoscopy with narrow-band imaging (M-NBI). METHODS: Various endoscopic and M-NBI findings of 286 SNADETs were retrospectively reviewed and compared between G- and I-types and histological grades. M-NBI findings were divided into four patterns based on the following vascular patterns; absent, network, intrastructural vascular (ISV), and unclassified. Lesions displaying a single pattern were classified as mono-pattern and those displaying multiple patterns as mixed-pattern. Lesions showing CDX2 positivity were categorized as I-types and those showing MUC5AC or MUC6 positivity were categorized as G-types based on immunohistochemistry. RESULTS: Among 286 lesions, 23 (8%) were G-type and 243 (85%) were I-type. More G-type lesions were located oral to papilla (91.3 vs. 45.6%, p < 0.001), and had protruding morphology compared to those of I-types (65.2 vs. 14.4%, p < 0.001). The major M-NBI pattern was ISV in G-type (78.2 vs. 26.3%, p < 0.001), and absent for I-type (0 vs. 34.5%, p = 0.003). Three endoscopic characteristics; location oral to papilla, protruding morphology, and major M-NBI pattern (ISV) were independent predictors for G-type. Mixed-pattern was more common in HGA/Ca than LGA for I-type (77.0 vs. 58.8%, p = 0.01); however, there was no difference for those in G-type. CONCLUSION: Endoscopic findings including M-NBI are useful to differentiate epithelial subtypes.

Initial tumor size and narrow-band image findings estimate growth speed in duodenal tumors.

INTRODUCTION: Recently, detection of superficial non-ampullary duodenal epithelial tumors (SNADETs) including adenomas and superficial duodenal carcinomas has increased. Various endoscopic treatment methods have also been reported for SNADETs, but there are few reports on the natural history. The aim of this study was to analyze factors related to tumor growth and determine the characteristics of SNADETs which need early therapeutic intervention. METHODS: A single-center, retrospective study was performed on medical records of 309 patients with SNADETs who underwent endoscopic or surgical resection between January 2010 and May 2021. Of these, 41 patients who were followed up for more than one year by endoscopy were analyzed. The primary outcome was analysis of the tumor growth speed. Secondary outcomes were the relationship between the tumor growth speed and mucin phenotype, tumor size and findings of magnifying endoscopy with narrow-band imaging (M-NBI). RESULTS: The observation period was 24 months (13-182). Tumor growth speed was 1.1 mm/year (0-21.6). Tumor diameter >10 mm at first detection (P=0.004; Odds ratio 19.5(2.03-186.96)) and mixed-type by M-NBI (p=0.036; Odds ratio 9.69(1.05-89.88)) were identified as risk factors of tumors growing at a rate of >3 mm/year. There was no statistically significant difference in the speed of tumor growth between the different mucin immunohistochemical phenotype. CONCLUSION: Initial tumor size and findings of M-NBI are useful to predict tumor growth and consider early intervention.

Clinical outcomes of the over-the-scope clip closure after duodenal endoscopic submucosal dissection: A multicenter retrospective study.

BACKGROUND AND AIM: Prophylactic closure with the over-the-scope clip (OTSC) after endoscopic submucosal dissection (ESD) of superficial non-ampullary duodenal epithelial tumors (SNADETs) has been reported to reduce postoperative adverse events (AEs). However, there are few evidences regarding AEs-associated factors and long-term outcomes of OTSCs. METHODS: From January 2011 to December 2020, 139 consecutive patients with SNADETs who underwent ESD followed by OTSC closure in five institutions were extracted in this retrospective study. The primary endpoint was the rate of postoperative AEs after prophylactic OTSC closure. The secondary endpoints were the complete closure rate, residual rate, and long-term AEs associated with residual OTSCs. RESULTS: The rate of complete closure of the mucosal defect was 97.3% (142) in 146 SNADETs, which were completely resected by ESD. Postoperative AEs, including delayed bleeding, delayed perforation, and localized peritonitis, occurred in 6.2%, 3.4%, and 2.1% of patients, respectively; however, all of the cases improved without surgical treatment. In the multivariate logistic regression analysis, the use of two or more OTSCs was a significant independent risk factor for postoperative AEs (odds ratio, 2.94; 95% confidence interval, 1.02-8.46; P = 0.046). The residual OTSC rate was 46.4% at 1 year postoperatively, and long-term AEs included duodenal erosions and ulcers associated with residual OTSCs. CONCLUSIONS: Prophylactic closure with OTSCs after duodenal ESD can provide acceptable short-and long-term outcomes for preventing postoperative AEs. However, multiple OTSCs were the independent risk factors of postoperative AEs due to the gaps between and near the OTSCs.

Long-Term Monitoring and Clinical Implications of Small Bowel Capsule Endoscopy in Patients with Crohn's Disease with Small Bowel Lesions: A Retrospective Analysis.

INTRODUCTION: Crohn's disease (CD) induces persistent inflammation throughout the gastrointestinal (GI) tract, potentially resulting in complications such as intestinal stenosis and fistulas, particularly in the small bowel. Small bowel capsule endoscopy (SBCE) is recommended for monitoring CD, especially when GI tract patency is maintained. This study aimed to retrospectively assess patients with CD who underwent SBCE to determine the timing of clinical changes and address the current lack of evidence regarding GI tract patency loss during CD treatment. METHODS: Of the 166 consecutive patients who underwent SBCE at our institution, 120 were followed up and included in this study. Forty-six patients were excluded due to colitis type or immediate treatment changes post-SBCE. This study focused on the primary and secondary endpoints, including the cumulative stricture-free rate of the GI tract, emergency hospitalization post-SBCE, and post-SBCE treatment strategies, at the discretion of the attending physicians. RESULTS: Demographic data revealed that the mean age of the study population was 43 years and that there was a male predominance (75%). The median disease duration was 12 years and the mean Crohn's Disease Activity Index was 98. During a 1,486-day observation period, 37% of patients experienced treatment changes. A Lewis score of >264 and perianal lesions were identified as independent risk factors for additional treatment needs. Emergency hospitalization occurred in 6% of patients and GI patency failure in 11%. Female sex and Lewis score>264 were associated with higher risks. GI patency rate declined 2 years after SBCE. CONCLUSIONS: For patients who experienced no treatment changes based on SBCE results, it is recommended to undergo SBCE monitoring at intervals of no longer than 2 years.

Analysis of Neuropeptides in the Intestinal Mucus of Patients with Ulcerative Colitis Using RNA Sequencing.

INTRODUCTION: Inflammation in ulcerative colitis (UC) originates in the colorectal mucosa. Transcriptome sequencing analysis of the colorectal mucosa allows the identification of potential neuropeptides related to local neurotransmission. The intestinal mucus lining the surface of the mucosa may harbor biomarkers of mucosal inflammation; however, this has not been sufficiently investigated, given the difficulty in obtaining human samples. We previously reported the feasibility of obtaining mucin samples for proteomic analysis by brushing during colonoscopy. Herein, we aimed to investigate the composition of the intestinal mucus and detect neuropeptides characteristic of UC. METHODS: Mucus and mucosal samples were collected from patients with UC from the colorectum in areas showing remission or active UC using a brush catheter and biopsy forceps during colonoscopy. RNA sequencing findings of mucus samples of active and remission areas were compared. RNA and protein expression levels of significantly upregulated neuropeptides were analyzed. RESULTS: Of the neuropeptides associated with UC, somatostatin (SST) was significantly elevated in areas of remission, according to RNA sequencing results of mucus and expression levels in mucus RNA and proteins. Conversely, SST expression in the mucosa was increased in the inflamed areas. Flow cytometry revealed that the fluorescence intensity of SST-positive cells in the remission zone was higher in the mucus than in the mucosa. CONCLUSION: SST expression in the mucus is considered to be an important factor associated with UC activity.

Monoclonal Antibodies Against Mature Interleukin-18 Ameliorate Colitis and Repair Goblet Cell Function.

BACKGROUND: Numerous biological interventions and small molecules are used to treat Crohn's disease; however, the effectiveness of these treatments varies largely. Non-responsiveness to biological therapies is associated with interleukin (IL)-18 gene polymorphisms and high IL-18 expression has been implicated in the pathogenesis of Crohn's disease. AIMS: The aim of this study was to elucidate the expression of precursor and mature IL-18 in patients with Crohn's disease who exhibited varied responses to cytokine-targeted treatments and determine whether selective inhibition of mature IL-18 offers a novel therapeutic avenue. METHODS: We generated a monoclonal antibody that specifically recognizes the neoepitope of caspase-cleaved mature IL-18. Expression of precursor and mature IL-18 was analyzed in patients with Crohn's disease. Anti-mature IL-18 monoclonal antibodies were intraperitoneally administered in an acute colitis mouse model, and the disease activity index, body weight loss, tissue pathology, proinflammatory cytokine expression, goblet cell function, and microbiota composition were assessed. RESULTS: Precursor and mature IL-18 expression was upregulated and goblet cell function was impaired in patients with Crohn's disease who were unresponsive to biological therapies. Administration of anti-mature IL-18 antibodies ameliorated induced colitis by repairing goblet cell function and restoring the mucus layer. CONCLUSIONS: The newly developed monoclonal antibody holds promise as a therapeutic alternative for Crohn's disease.

Gastric ectopic pancreas with a pseudocyst.

Ectopic pancreas (EP) is defined as pancreatic tissue that lacks anatomical or vascular connections to the normal pancreas. EP is generally asymptomatic and is detected incidentally during endoscopy. However, due to pseudocyst formation, inflammation, or malignant transformation, it may cause non-specific gastrointestinal symptoms, such as abdominal pain, abdominal discomfort, nausea, vomiting, and bleeding. Pseudocyst formation in EP may result from the retention of exocrine secretions in the absence of connections between the glandular epithelium and gastric lumen. We herein report a case of EP with a pseudocyst associated with epigastric pain. EP with a pseudocyst, although rare, needs to be considered in a differential diagnosis of cystic lesions of the stomach.

CH3 CN@open-C60 : An Effective Inner-Space Modification and Isotope Effect Inside a Nano-Sized Flask.

Despite several small molecules being encapsulated inside cage-opened fullerene derivatives, such species have not considerably affected the structures and properties of the outer carbon cages. Herein, we achieved an effective inner-space modification for an open-cage C60 derivative by insertion of a neutral CH3 CN molecule into the cavity. The CH3 CN@open-C60 thus obtained showed an enhanced polarity, thus affording an easy separation from a mixture containing the empty cage by column chromatography on silica gel, without the preparative HPLC that was needed for previous cases. The less negative reduction potentials with respect to those of empty cage reflect the decreased energy level of the LUMO, which is supported by the DFT calculations. NMR spectroscopy, single-crystal X-ray analysis, and theoretical calculations revealed that both the presence of the encapsulated CH3 CN and cage deformation caused by the CH3 CN play an essential role in the change of the electronic properties. Furthermore, the favored binding affinity of deuterated acetonitrile CD3 CN with internal C60 surface is discussed.

Factors Related to Delayed Adverse Events of Endoscopic Submucosal Dissection in the Duodenum.

INTRODUCTION: Endoscopic submucosal dissection for duodenal neoplasms (D-ESD) is considered a technically demanding procedure regarding the high risk of delayed adverse events. Data regarding optimal managements of ulcers after D-ESD are lacking. METHODS: A retrospective analysis was performed on consecutive 145 cases of D-ESD for superficial nonampullary duodenal epithelial tumors at a single referral center. Factors related to delayed adverse events and the healing process of ulcers after D-ESD were analyzed. RESULTS: Complete ulcer suture after D-ESD was performed in 128 cases (88%). Two delayed perforation occurred among cases with incomplete suture. Delayed bleeding occurred in 8 cases (6%) within 3 weeks. The ulcer closure rate at second-look endoscopy (SLE) was significantly low among cases with delayed bleeding (12.5% vs. 75%, p = 0.001). The bleeding rate before SLE was significantly high among patients who did not have complete ulcer closure after D-ESD (0.8% vs. 12%, p = 0.036). The ratio of lesions located in the second oral-Vater was significantly low among ulcers re-opened at SLE (38% vs. 14%, p = 0.044). Proton-pump inhibitors (PPIs) were administered for a median of 7 weeks (range 1-8 weeks). At 3 weeks, active ulcer stages were observed in a few cases, and healing or scarring was observed in most cases. CONCLUSIONS: Complete ulcer suture was related to decreased risk of delayed adverse events after D-ESD. From the bleeding period and healing process of D-ESD ulcers, the minimum required length of PPI may be 3 weeks after D-ESD.

Superficial non-ampullary duodenal epithelial tumors now: endoscopic diagnosis and therapy.

With the recent increase in the frequency of duodenal tumor detection, significant progress has been made in endoscopic diagnosis and treatment. Although the first guidelines were issued in Japan, patient treatment varies widely among institutions. There is a need for improving the quality of endoscopic diagnosis and more curative and safer treatments. Biopsy is the standard diagnostic method; however, the diagnostic accuracy of endoscopic biopsy is not so high. Therefore, the differentiation of superficial non-ampullary duodenal epithelial tumors from non-neoplastic lesions is being developed. The incidence of lymph node and distant metastases of duodenal epithelial tumors is extremely rare in intramucosal carcinomas, and they are considered good candidates for endoscopic treatment if the technical difficulties can be resolved. Adverse events associated with endoscopic treatment are greatly reduced at advanced facilities through novel resection and closure methods, and further improvements are expected in the future. Clarifying the risk of metastatic recurrence may lead to the development of more appropriate treatments and curative resection criteria.

Endoscopic submucosal dissection using a novel thin-therapeutic endoscope for superficial esophageal squamous cell carcinoma with severe stricture at the pharyngoesophageal junction.

When performing endoscopic submucosal dissection (ESD) beyond stenoses, there have only been two choices: balloon dilation until a conventional therapeutic endoscope passes through or the use of an ultrathin endoscope. However, balloon dilation has a risk of perforation and an ultrathin endoscope limits the devices that may be used. The novel thin-therapeutic endoscope has an outer diameter of 7.9 mm and instrument channel diameter of 3.2 mm; therefore, there are no restrictions on the ESD device that may be used, and the procedure may be performed in the same manner as regular ESD. We herein report a case in which the thin-therapeutic endoscope was useful for esophageal ESD beyond a stenosis.

Suturing of a mucosal defect after gastric endoscopic submucosal dissection using a combination of an anchor pronged clip and conventional clips.

Suturing of a mucosal defect after gastric endoscopic submucosal dissection (ESD) reduces the incidence of adverse events and shortens hospitalization. However, post-ESD mucosal defects are circular, large, and with a thick mucosal layer, which are difficult to suture using conventional clips alone. The MANTIS Clip (Boston Scientific Japan, Tokyo, Japan) is a reopenable, rotatable through-the-scope clip designed for large defect closure. It uses anchor prongs to securely grasp wound edges. The initial use of the MANTIS Clip significantly reduces mucosal defects, which then allows for easy suturing with conventional clips. We herein report a case in which the MANTIS Clip was useful for suturing a mucosal defect after gastric ESD.

Novel endoscopic approaches using the endocytoscopy for the target biopsy in esophageal eosinophilia.

BACKGROUND AND AIMS: Multiple biopsies are recommended for the diagnosis of eosinophilic esophagitis (EoE) because inflammatory changes are frequently patchy. Reports on EoE using endocytoscopy (ECS) are limited. This present study aimed to assess if diagnostic yield improves by adding ECS on conventional white light imaging (WLI) in patients with esophageal eosinophilia (EE). METHODS: A total of 284 biopsy specimens from 71 patients with a known diagnosis of EE were enrolled and divided into the WLI group (156 specimens) or the ECS group (128 specimens). Four biopsies from 5 and 10 cm proximal to the esophagogastric junction were taken from each patient. In the ECS group, the biopsy was performed where bilobed nuclei were observed. The biopsy sensitivity for EE, eosinophil count of a single specimen and the biopsy sensitivity of each endoscopic finding were evaluated between both groups. RESULTS: The sensitivity of a single biopsy specimen was higher in the ECS group than that of the WLI group (62.5 vs. 41.7%, P < 0.001). In addition, the median eosinophil count in the ECS group was significantly higher [19 vs. 6.5/high-power field (HPF), P < 0.001]. For each endoscopic finding, ECS-based biopsy had higher sensitivity than that of WLI in the diagnosis of edema (33.1 vs. 11.3%, P = 0.007) and linear furrows (75.8 vs. 52%, P = 0.005). CONCLUSION: This study showed that adding ECS to WLI improved the biopsy sensitivity and eosinophil detection in patients with EE.

An H2 O2 Molecule Stabilized inside Open-Cage C60 Derivatives by a Hydroxy Stopper.

An H2 O2 molecule was isolated inside hydroxylated open-cage fullerene derivatives by mixing an H2 O2 solution with a precursor molecule followed by reduction of one of carbonyl groups on its orifice. Depending on the reduction site, two structural isomers for H2 O2 @open-fullerenes were obtained. A high encapsulation ratio of 81 % was attained at low temperature. The structures of the peroxosolvate complexes thus obtained were studied by 1 H NMR spectroscopy, X-ray analysis, and DFT calculations, showing strong hydrogen bonding between the encapsulated H2 O2 and the hydroxy group located at the center of the orifice. This OH group was found to act as a kinetic stopper, and the formation of the hydrogen bonding caused thermodynamic stabilization of the H2 O2 molecule, both of which prevent its escape from the cage. One of the peroxosolvates was isolated by HPLC, affording H2 O2 @open-fullerene with 100 % encapsulation ratio, likely due to the intramolecular hydrogen-bonding interaction.

Comparison of Endoscopic Ultrasonography and Conventional Endoscopy for Prediction of Tumor Depth in Superficial Nonampullary Duodenal Epithelial Tumors.

BACKGROUND: The utility of endoscopic ultrasonography (EUS) in predicting tumor depth among superficial nonampullary duodenal epithelial tumors (SNADETs) is unclear. The aim was to compare EUS with conventional endoscopy (CE) for the evaluation of tumor invasion of SNADETs. METHODS: A retrospective analysis was performed on consecutive 174 lesions/169 patients with duodenal dysplasia or adenocarcinoma with invasion up to submucosa who underwent both CE and EUS before endoscopic (n = 133) or surgical (n = 41) treatment. Endoscopic staging by CE was performed based on the characteristic endoscopic criteria of submucosal invasion (irregular surface, submucosal tumor [SMT]-like marginal elevation, and fusion of converging folds). The diagnostic performance of each test was compared with the final histology. RESULTS: The sensitivity and accuracy of estimating the depth were higher for CE compared to that of EUS (99.4% vs. 89.4%, p < 0.01 and 97.7% vs. 87.9%, p < 0.01, respectively). Univariate analysis of endoscopic factors revealed that tumor diameter, red color, SMT-like appearance, and hypoechogenicity were factors related to advanced histology. Multivariate analysis revealed that the presence of SMT-like appearance based on CE was an independent factor to predict submucosal invasion (p = 0.025). Gross morphology of the combined type was associated to incorrect diagnosis of EUS (p = 0.007). Among 3 cases in which EUS overestimated the tumor depth, carcinoma extension in submucosal Brunner's gland or nontumorous submucosal cystic dilation was observed. CONCLUSION: EUS may not be necessary, and CE may be sufficient for determining the optimal therapeutic strategy for SNADETs.

Effects of steroid use for stenosis prevention after endoscopic submucosal dissection for cervical esophageal cancer.

BACKGROUND AND AIM: Esophageal stenosis is a serious complication after endoscopic submucosal dissection (ESD) for thoracic esophageal cancer (TEC), and steroid has been applied for stenosis prevention. However, the rate of stenosis and effect of steroid for ESD of cervical esophageal cancer (CEC) remain unknown. The aim was to clarify the rate and managements of post-ESD stenosis for CEC. METHODS: A total of 325 lesions with 272 patients who underwent ESD for esophageal cancers were enrolled and were divided to the CEC group (43 lesions) or the TEC group (282 lesions). Patient characteristics, clinicopathological features, procedure-related outcomes of esophageal ESD, stenosis rate and clinical outcome of steroid use cases were evaluated. RESULTS: More patients in the CEC group received preventive steroid treatment compared to the TEC group (37.2% vs 14.5%, P = 0.001). The rate of post-ESD stenosis tended to be higher in the CEC group (11.6%) than in the TEC group (6.7%). For cases of 3/4 ≤ of circumference, local injection with oral steroid had lower stenosis rate than local injection only in both groups (CEC 40% vs 100%, TEC 30.7% vs 56.3%). More sessions and longer duration of dilation were needed to release the stenosis in the CEC group (20 times vs. 5 times, P = 0.015; 196 days vs. 55 days, P = 0.043). CONCLUSION: The post-ESD stenosis rate of CEC tended to be higher than that of TEC. More intensive preventive measures for post-ESD stenosis may be needed for CEC than TEC.

Fecal incontinence and oral regurgitation during duodenal endoscopic submucosal dissection using the water pressure method.

OBJECTIVES: Endoscopic submucosal dissection (ESD) in the duodenum is challenging. The water pressure method (WP-ESD) has been developed with a decreased rate of perforation. However, details of perioperative adverse events of WP-ESD are unknown. The purpose of this study was to clarify the frequency and related factors of fecal incontinence and oral regurgitation during WP-ESD. METHODS: A chart-based retrospective analysis was performed on 43 patients who underwent duodenal WP-ESD. The saline volume given into the body was calculated in all cases. All adverse events during WP-ESD until 6 weeks were extracted, and factors related to intraoperative fecal incontinence or oral regurgitation were analyzed. The frequency of fecal incontinence and oral regurgitation was also compared to those of 83 conventional ESD cases. RESULTS: In WP-ESD, intraoperative fecal incontinence occurred in 12 (28%), oral regurgitation in six (14%), and aspiration pneumonia in one patient. For fecal incontinence, the infusion speed (saline volume divided by resection time) around 17 mL/min was a significant factor in multivariable analysis. For oral regurgitation, only tumor size was a significant factor in univariate analysis (P = 0.027). Significant difference was observed in the frequency of fecal incontinence between WP-ESD and conventional ESD (28% vs. 0%, P < 0.001), but no difference was observed in oral regurgitation or aspiration pneumonia. CONCLUSIONS: Intraoperative fecal incontinence is a unique adverse event of WP-ESD related to the infusion speed. WP-ESD did not pose a risk for oral regurgitation, but we should be aware of the risk in large tumor cases.

Diarylethene-Powered Light-Induced Folding of Supramolecular Polymers.

Helical folding of randomly coiled linear polymers is an essential organization process not only for biological polypeptides but also for synthetic functional polymers. Realization of this dynamic process in supramolecular polymers (SPs) is, however, a formidable challenge because of their inherent lability of main chains upon changing an external environment that can drive the folding process (e.g., solvent, concentration, and temperature). We herein report a photoinduced reversible folding/unfolding of rosette-based SPs driven by photoisomerization of a diarylethene (DAE). Temperature-controlled supramolecular polymerization of a barbiturate-functionalized DAE (open isomer) in nonpolar solvent results in the formation of intrinsically curved, but randomly coiled, SPs due to the presence of defects. Irradiation of the randomly coiled SPs with UV light causes efficient ring-closure reaction of the DAE moieties, which induces helical folding of the randomly coiled structures into helicoidal ones, as evidenced by atomic force microscopy and small-angle X-ray scattering. The helical folding is driven by internal structure ordering of the SP fiber that repairs the defects and interloop interaction occurring only for the resulting helicoidal structure. In contrast, direct supramolecular polymerization of the ring-closed DAE monomers by temperature control affords linearly extended ribbon-like SPs lacking intrinsic curvature that are thermodynamically less stable compared to the helicoidal SPs. The finding represents an important concept applicable to other SP systems; that is, postpolymerization (photo)reaction of preorganized kinetic structures can lead to more thermodynamically stable structures that are inaccessible directly through temperature-controlled protocols.